Calcining apparatus



Feb. 17, 1953 J. R IZ 2,628,829

CALCINING APPARATUS Filed Oct. 25, 1947 2 Sl-lEETS-SI-IEET 1 INVENTOR.JOSEPH J. RUIZ- Q' TORNEYS- J. J. RUIZ CAL CINING APPARATUS Feb.- 17,1953 Filed 001;.25, 1947 INVENTOR. JOSEPH J. RUIZ BY m9 ATTOENEY.

Patented Feb. 17, 1953 CALCINING APPARATUS Joseph J. Ruiz, Cleveland,Ohio, assignor to Basic Refractories, Inc., Cleveland, Ohio, atcorporation of Ohio Application October 25, 1947, Serial No. 782,099

Claims.

This invention relates to calcining apparatus, and in its more specificapplications to kilns for burning limestone, dolomite, and the like.

Commonly, lime kiln apparatus takes the form of a vertical shaftconstruction operating at substantially atmospheric pressure, the exitgas from the top passing ofi to compressors which are ordinarilyrequired to assure draw-off and raise the pressure sufiiciently to beapplied in various usages. Where the fuel is charged in admixture withthe limestone, it is customary to provide combustion air by a blowerconnection at the bottom of the kiln. With such equipment, the burden ofcompressing the outlet gas is considerable, and there are difficultieswith compressors which. have to operate on gas containing sulphurdioxide and on gas which even after going through a scrubber depositssubstances oncylinder heads and valves and gives rise to unduly heavymaintenance and repair costs. In accordance with the present invention,a construction is had in which the calcining operation can be conductedunder pressure, and allow the outlet gas to accordingly proceed atdesired pressure without compressor requirement, and such as to be thusdirectly available for desired uses. All of the compressor actionrequired is positioned at the air-supply inlet, and by this theoperating pressure for the kiln and the outlet pressure of the gas maybe controlled. Other objects and advantages of the invention will appearfrom the following description.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of but afew of the various ways in which the principle of'the invention may beemployed.

In said annexed drawings:

Fig. 1 is a side elevational View partly in section, showing oneembodiment of the invention;

- Fig. 2 is an enlarged sectional view of the charging and gas-lock endof the structure; and

Fig. 3 is an enlarged sectional view of the discharge and air-lock endof the construction.

In "general, the construction involves an elongated container K capableof withstanding the desired high gas pressures as well as the load ofstone, and it may comprise a steel shell lined -with refractorybrickwork and having a conical .top 2 and conical bottom 3. Mounted inthe top 2 is a conduit for inlet of material, and which, as shown inFig. 2, may involve a stationary pipe 4 with a valve leading from thecharging hopper 6, which in turn through a valve 1 communicates with acollecting hopper 8. The lower end of the pipe 4 sets in a stuffing boxIt], and in relation with a sleeve II which is rotatable and connectedwith the gear 12 driven from pinion [3 by the drive motor I4 and gearreducer I5. The sleeve II is mounted with suitable thrust and journalbearings, and

where passing through the top of the cone 2 through the outlet 20 andthence proceeds through conduit 2| to desired cleaning means, as

for instance a scrubber 22, and thence by conduit 23 to a desiredpointof storage or usage.

From such construction, it is seen that the top of the calciningchamber, While permitting free ,outflow of the gas, may receive feed ofmaterial. And, to further prevent interference with the gas pressure,the charging hopper B is provided with gas-lock means, involving theoutlet valve 5 and the inlet valve 1, and by operation of these valvesin alternation, the valve 5 being closed when the valve 1 is opened, andvice versa, the desired high operating pressure may be maintained in thekiln.

At the bottom a rotatable discharge cone 25 having a spiral stepsurface, within a fixed annular platiorm 26, regulates the retention;and in the rotation of the cone the burned lime or other product ispassed out through the annular opening 21' and falling down along thecone bottom 3, may be passed through the valve 30 to the dischargehopper 3|, whose outlet is guarded by a valve 32. Here again, the inletand outlet valves for this hopper are operated in alternation. When thevalve 311 is opened, the valve 32 is in closed position, and vice versa.The cone 25 is desirably mounted on a set of rollers 34 on a raceway 35,and is driven by an attached ring gear 36 from a pinion 37 on a driveshaft 38 which passes through a stuffing box 39 in the cone bottom 3.The shaft 38 is driven, for instance, by a motor 43 and gear reducer 4|.

Entering through the cone bottom 3 is a con- I duit 44 from a source, ofair under pressure, for

instance a compressor 45 driven by a motor 46.

As apparent from this construction, high pressure air is supplied at theoutlet end of the calcining chamber, and discharge of the calcinedproduct may be carried on Without interruption and without interferingwith the maintenance of the operating pressure of the apparatus.

The material supplied t the calcining chamber may be provided by anysuitable means. For instance, conveniently there may be a proportioningcharge-former involving a crushed stone sup- .ply 50 and a fuel supply5| feeding to a conventional weighing and mixin charger 52, and thenceto a skip-hoist bucket 53 which is controlledly drawn to the top of itsframe and dumped into the collector hopper 8. As seen, the materialcalcined may be of various character,

A and most commonly, for instance, may be considered as limestone,dolomite, and the like. The fuel may be any suitable solid carbonaceousfuel, for instance, coke. In the customary operation of lime burning byadmixed fuel and combustion at substantially atmospheric pressure, thestone which is fed, and the fuel, must be in large size,

not less than two inches, to permit adequate draft. With the presentconstruction, however,

on thecontrary, the dimension of the material fed may be very muchsmaller, and with very material advantages. Thus, stone and coke sizedto less than'one inch isreadily operated. 'With the supply or collectinghopper 8 provided with the desiredstoneahd fuel, the valve 1 is opened(the valve 5 of course being in closed position as normal) and thecharge is run into the hopper 6, whereupon the valve 1 is closed and thevalve 5 is opened, and the motor I4 being in operation turning the coneor distributor H, the material is fed 'down into the calcining chamber.When the chamber is filled and in stable operation, with high pressureair being forced in from the compressor 45, and combustion proceeding incontrolled condition, the calcining chamber as a whole .presents threezones of action. In the bottom zone D, Fig. 1, the material coming tothe discharge cone is the calcined lime or other prod- ;uct, the fuelhaving been all burned out, and this highly heated product is passingdowncountercurrently to the flow of incoming air Under pres sure, thecalcined product being thereby progressivel'yrcooled down such that itcomes to final discharge at a relatively cool temperature, the heat "ofthe construction is very high, substantially all the heat of combustionbeing used in the calcining-and without wastage inthe discharged productand'g-as.

"Desirably, a device responsive to the top level of'the material in thekiln K, suchas an indicator test rod 81 riding on the top of the mass inthe calcining chamber, may actuate suitable electric switch mechanism asavailable commercially to operate insequence the valves 5, 'i, and 30,32,

and the drive motor It, as referred to more in detail herein-after. Aschedule in which the drive motor 40, however, operates the dischargecontinuously is desirable, as such uniformity insures against unevennessof movement through the kiln; and thereby possible trouble from hangingor arching of the kiln contents may be obviated. In such operating cyclealso, as a part of the refinement the pressure in the charging hopper 6may be gas-equalized, and thus when the valve 7 is closed on a charge inthe hopper, a gas-feed valve Gil supplied by pipe 5! from the gasoutlet, may introduce gas to the hopper 6 in equalization with that ofthe kiln pressure, the valve 651 being then vented to the outlet 62 asthe communication to the hopper 6 is closed. In similar manner, in thecycle, when the hopper 3! is filled from the valve 30 and the valve 39is closed, the valve 84 is opened to introduce air from the conduit 4into equalization of pressure, the valve 64 being then closed, withventing to outlet 65, all as referred to more in detail hereinafter.Electrically operating relay controls are known and commerciallyavailable.

The actual pressure selected for operation is determined to quite anextent upon the pressure desired for the carbon dioxide gas at its pointof usage. Economic considerations also enter. Illustratively, a pressureof 60 lbs. p. s. i. abs. may be mentioned, but obviously it may begreater or less as desired. Apparatus thus operating under pressureresults in many advantageous features. The cost of compressor power isreduced, inasmuch as compression of exit gas as customarily practicedinvolves more power than that required to operate the air compressors inthe present apparatus, and, besides, there is a very substantial savingin that whereas compressors operatin on kiln discharge gases are subjectto rapid deterioration, the compressor here operating on clear air issubject to no such disability. Again, whereas under common practice thestone to be calcined must be of two-inch size or more, with the presentapparatus much smaller size stone, and fuel, is desirable, and since thepressure drop of gases flowing through a bed of broken solids isproportional to the density of the gas and to the square of the gasvelocity, with the total pressure as here raised, the over-all effect isto lessen the pressure drop, and since the pressure drop or loss is alsoinversely proportional to the size of the stone, it is to be seen thatfor a kiln operating at 60 lbs. abs. pressure, stone onequ-arter thesize of that for a kiln operated at atmospheric pressure can be used,and yet the power required to force the. air and gases through the kilnis low. The size of stone could in fact be down to one-sixteenth thatfor the conventional atmospheric pressure operation. With the ability touse smaller size stone, there is also an improvement in the uniformityof lime burning, reducing the amounts of unburned cores and over-burnedstone. To provide the best conditions for the radiation of heat from theburning fuel to the stone, the kiln charge should contain approximatelyone piece of fuel for each piece of stone, and with the small sizes ofmaterial applicable in the present apparatus, a saving in fuel cost ishad, since coke costs decrease with the particle size, and here evencoke breeze can be used, this being of low-cost particularly, incontrast to lump coke. The capacity or the tonnage of stone that can becalcined in a given kiln volume depends on the stone surface area and onthe weight of air and gases flowing through it. With operation underpressure and small stone size, the stone are-aper volume is increased,thereby increasing the heat transfer rate from the gases to the stoneand increasing the capacity throughput of the kiln. Independently of thestone size also, the heat transfer rate between the gases and the stone,and between the calcined product and the incoming air is increased inpressure operation. The heat transfer rate and kiln capacity increase asthe weight or mass flow for a given cross-sectional area is increased,and as the gas pressure is increased there is an in crease in itsdensity or mass per volume. For a given linear gas velocity andpressure-loss through the kiln, operating under pressure gives anincrease in kiln capacity. The rate of combustion of fuel also increaseswith the pressure, being a function of the partial pressure of oxygen.

Also, with a kiln operating at high pressures, the volume and velocityof gases are reduced to a point where the smaller sized fuel can be usedwithout being blown out by the gas. It will be realized that the maximumlimiting rate of operation of. a vertical type kiln, for a givencrossseotion-al area, would be reached when the gas flow (linearvelocity) becomes so high as to carry the small solid particles out ofthe charge. By increasing the operatin pressure and gas density,.agreater amount of air and gas measured on weight basis (mass) can bemade to flow through the kiln without danger of blowing the small solidparticles out, and in this way the amount of fuel burned for a givencross-sectional area can be increased; also the heat transfer ratebetween the gas and stone and the burned lime and incoming air can bematerially increased with increase of mass (weight) flow of gases pergiven cross-sectional area. In other words, even with the same siZe ofstone as conventionally employed, if the operating pressure be increasedit increases the capacity of the kiln.

As seen, a pressure kiln may be smaller in size for a given production,and with such reduction in size and external surface there is acorrespondin reduction in heat loss therefrom,

and correspondingly a decrease in fuel requirements to such extent. Asthe calcination of carbonates of calcium and magnesium follows closelythe thermo-dynamic properties of boiling water, the temperatureremaining constant during the calcination, and being a function of thepartial pressure of the carbon dioxide, as the pressure and temperatureof the carbon dioxide are increased, the heat required decreases, and

pressure-operation results in a corresponding decrease in fuelrequirement.

required'per ton-of stone calcined, correspond-- ingly the amount ofnitrogen input is reduced, and the per cent of carbon dioxide in theexit gas is increased.

Since less air is Sincea calcining apparatuson the lines of the presentconstruction is capable of forwarding its contents at a much more-rapidrate than the "customary type of apparatus, centralized and automaticcontrol becomes possible and is of partioular' value. Thus, a mastercontroller M, Fig.

' 2, and which can be a relay set of electric switches or a "programswitch consisting of a motordriven cam shaft with cams set to operatesuccess'ive switches in sequence and timing, all as commerciallyavailable, may be applied, such that as initiated by a'contact-80 inassociation 'with the stone-level indicator 8| riding on the top of thematerial in the kiln,-will first, through electrical connection 82,start thestone and coke proportioning feeders 50, 5|, and the skip hoist53 to bring material to the hopper 8, and in proper sequence thenoperate the electromagneticall'y-actuated valve 83 to openthe valveil bythe fluid-pressure cylinder 84 (usingair or liquid), the valve 5 beingin closedposition as controlled by electromagnetically actuated valve 85and the fluid-pressure cylinder 86; and in relation, theelectromagnetically actuated valve 81 is also controlled to vent thevalve 60 by the fluid pressure cylinder 88. By such sequence it is seenthat the valve 5 is opened to the calcining chamber. In every phase ofoperation, the valves 5 and l are in such sequential control that theycannot be both opened at the same time but operate in alternation,thereby eliminating danger of accident. The master controller M also inits sequence puts thedrive motor [4 into action when the valve 5 isopened, so as to operate the distributor IT as the material flows downfrom the charging hopper 6 through the valve 5 to the calcining chamber.Analogously, the lime-level indicator 90, Fig. 3, riding on top ofmaterial in the discharging hopper 3|, actuates a contact 8! to start amaster controller M', which may be of similar character as thecontroller M, to. sequentially operate the electromagnetically actuatedvalve 92 for the fluid pressure cylinder 93 to open the valve 39, thevalve 32 being closed through the action of electromagnetically actuatedvalve 94 and fluid-pressure cylinder 95; and in relation, theelectromagnetically actuated valve 96 and its dependent fluid pressurecylinder 9! opens the three-way valve 64 preliminarily to the opening ofvalve 30 so that air pressure from the conduit 44 may equalize thedischarge hopper 3| to the calcining chamber pressure before the valve32 is opened. After the hopper 3| is filled through the open valve 30,the controller M in the further phase closes the valve 30, therebyshutting off communication to the calcining chamber, and then ventsvalve 64 to the atmosphere vent pipe 65, and then finally opens thedischarge valve 3-2 to allow the calcined product to discharge. Theoperation of the master controller here again is such that the valves 30and 32 are never opened at the same time, but always in alternation,thereby preventing accident. In further detail, thefiuid-pressurecylinder 93 for the valve 30 has a limit switch 98 arranged to close anelectric circuit to actuate solenoid valve 99 into open position whenthe valve 30 reaches its closed position; and similarly the fluidpressure cylinder 95 for the valve 32 has a limit switch I08. to closethe electric circuit torjset solenoid valve liil into open positionwhenvalve 32 reaches closed position. The operating fluid for the fluidpressure cylinders is supplied through pipe f. The fluid pressurecon-trolto the cylinders 84, 86, Fig. 2, is analogous, each of thesecylinders having its limit switch like those of cylinders 93, 95, andthe pressure-fluid bein supplied through pipes f.

A thermostat t, Fig. 1, in the gas space at the 'top of the calciningchamber, actuates an elecmaximum operating safe temperature for thelime-drawing mechanism.

The air-flow controller 68 for regulating the speed of the motor 46,thereby maintaining the required quantity of air and so regulating therate of lime andkiln gas production, may be of diaphragm or other typecommercially available. A temperature-limit switch 1:,Fig. 1, in the gas7 space atithetop of the calciningzchamber, .is set to stop :the motorlliii .in the event the kiln top itemperature exceeds afnraximum safeoperating temperatureat thegas outlet.

In the. valve-control arrangement as noted, it is seen thatthe.charginghopper 6 always has its pressure preliminarily equalized tothat of the space with which it :is to be put in communication; as themaster controller M actuates the valve 8-] and fluid pressure cylinder88 to open thevalve 16s to atmospheric-vent 62 and equalize thehopperpressure with that of the atmosphere and collecting hopper 8before the inlet valve 1 is opened by control-valve 83 and fiuidpressurecylinder 84, and again before the. discharge valve is opened :to thecalcining chamber the valve 611 is opened :to the gas connection '65 andthe ca'l'c'in'ing chamber, whereby the pressure in the -latter isequalized into the hopper B and accidents from unequal pressures areavoided.

Similarly with discharge hopper 3| the master controller M .actuates thecontrol-valve 96 and 'fluid pressure cylinder 91 to open the valve 65between the-compressed airpipe M and the hopp'er 3| before the valve isopened to allow calcined product to flow in from the calcining chamber,and the valve 64. is opened between the discharge hopper .31 and theatmospheric-vent 65 to equalize'the pressure to atmospheric before "theoutlet valve 32 is opened to discharge the product to the atmosphere.

Other modes of applying the principle of the invention may be employed,change being made :as reg-ards the detail described, provided thefeatures stated in any of the: following claims, .or the equivalent ofsuch, :be -.employed.

1 therefore particularly pointout and distinctly claim as my invention:

1. In calcining apparatus having .a vertical calcining chamber and acharging hopper thereforwith an inlet valve and an outlet valve, astationary outlet pipe from the outlet valve, a rotatable sleeve incommunication for passing materiail'into the top of. said'chamber, drivemeans for rotating said sleeve, 2. stufiing box between said sleeveandsaid pipe, at stufiing box between :said sleeve and thecalciningchamber, distributsing means carried by the lower end of said sleeve torrotation therewith, said distributing means being within the upper end'of the calcining chamber and continuously rotatable when the outletvalve is open for passing material to said chamber so as to evenlydistribute the material *withinthe chamber, discharge means at thebottom of the chamber, a discharge hopper below said discharge'mean'shaving an inlet valve and an outlet valve, and means for supplyingcompressed air to the bottom of said chamber, said distributing meansincluding a plate of cone-like form with the apex thereof pointinupwardly and with the bottom edge of the plate being spaced from the"vertical axis thereof byamounts continuously varying around the bottomedge.

2. In calcining apparatus :having a vertical calcining chamber and acharging hopper therefor with an inlet valveand anoutlet valve, astationary outlet pipe from the outlet valve, a rotatable sleeve incommunication for passing material into the top of said chamber, drivemeans tor rotating said sleeve, a stuffing box between said sleeve andsaid pipe, a stuifing box between said sleeve and the calcining chamber,distributing means carried by the lower end of said sleeve for rotationtherewith, .said distributing means being within the upper end of thecalcining cham'ber rand continuously rotatable when the :outlet valve:is open .-for passing material to said chamber .so as to evenlydistribute the material withinthe chamber, discharge means at the bottomof :the chamber, a discharge hopper below said discharge means having aninlet valve and an outlet valve, and means for supplying compressed. airto the bottom of said chamber, said distributing means including a plateof cone-like form with the apex thereof pointing upwardly and juxtaposedto the outlet end of the sleeve, the axes of the sleeve and thecone-like plate being substantially coincidental so that the materialpassing from the sleeve is evenly distributed over the plate, and thebottom edge of said plate being spaced from the axis of the plate byamounts continuously varying around the bottom edge.

3. In calcining apparatus having a vertical calcining chamber and acharging hopper therefor with an inlet valve and an outlet valve, astationary outlet pipe from the outlet valve, a rotatable sleeve incommunication for passing material into the top of said chamber, drivemeans for rotating said sleeve, distributing means carried by the lowerend of said sleeve .for rotation therewith, said distributing meansbeing within the upper end of the calcining chamber and-continuouslyrotatable when the outlet 'valveis .open for passing material to saidchamber so as to evenly distribute the material within the chamber,rotary discharge means at the bottom of said chamber, said rotarydischarge means including a cone-like member having the periphery of itsbase spaced from the chamber wall so as to define a passageway betweenthe periphery of the cone-like member and the chamber 'wall for thedischarge of the product, said cone-like member having its upper surfaceformed of a downwardly and outwardly substantially vertical, spirallystepped surface joined by a substantially fiat upwardly facing spiralsurface so as to control the discharge descent of the product duringcooling of the product by the incoming air,-a discharge hopper belowsaid discharge means and having an inlet valve and an outlet valve, andmeans .for supplying compressed air to thebottom of the chamber.

,4. In calcining apparatus according to claim 3, 'said last recitedmeans including an air inlet pipe theinner end of which isdisposed-below the center of 'saidrotary cone-like member.

5. In calcining apparatus having. a vertical calcining chamber. and acharging hopper therefor with an inlet valve .and an outlet valve, a

stationary outlet pipe from the outlet valve, a rotatable sleeve incommunication for passing material into the top of said chamber, drivemeans forrotating said sleeve, a stufiing box between said sleeve andsaid pipe, a stufiing box between said sleeve and the calcining chamber,distributing means carried by the lower end of said sleeve for rotationtherewith, said distributing means being within the upper end of thecalcining chamber and continuously rotatable when the outlet valve isopened for passing material tosaid chamber so as to evenly distributethe material within. the chamber, discharge means at the bottom of thechamber, a discharge hopper below said discharge means having an inletvalve and an outlet valve, and means for supplying compressed air to thebottom of said chamber, said distributing means including a plate ofconeellike form with the apex thereof pointing :upwardly and with thebottom edge of the plate being spaced from the vertical axis thereofbyamounts continuously varying around the bottom edge, and material-heightsensitive means in said discharge hopper operable to admit equalizingair pressure from the calcining chamber, then to open said inlet valveto the discharge hopper to fill the latter with the material from saidchamber, and then to close said inlet valve to the discharge hopper andvent the discharge hopper to the atmosphere and finally to open theoutlet valve of said discharge hopper.

JOSEPH J. RUIZ.

\ REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,119,280 Herrick Dec. 1, 19141,317,603 Steiger Sept. 30, 1919 1,581,724 Duckham Apr. 20, 19261,805,151 Reed May 12, 1931 Number iii Number 20 115,439 343,682 554,182

10 Name Date Swords June 2, 1931 Poole Jan. 10, 1933 Whitecomb et al,July 11, 1933 Gillette Sept. 26, 1933 Whitcomb Sept. 26, 1933 BergerDec. 26, 1933 Dienst Mar. 9, 1937 Haas May 18, 1937 Smith Oct. 19, 1937Davis Sept. 30, 1941 Azbe Feb. 27, 1945 Moher Oct. 8, 1946 EllerbeckOct. 19, 1948 Sherban June 13, 1950 Davis Aug. 29, 1950 FOREIGN PATENTSCountry Date Austria Dec. 2'7, 1929 Great Britain Feb. 26, 1931 GreatBritain June 23, 1942

